Traditionally, electrical power has been generated in large, centralized plants powered by fossil fuels, nuclear fission or flowing water, for example. Input fuel to such large scale power generation requires oil or coal, for example, which may not be readily available in all areas of the world.
Energy harvesting or energy scavenging from existing environmental sources has become an interest due to dwindling natural resources around the world. Energy harvesting is a process by which energy is derived from external sources (e.g., solar power, thermal energy, wind energy, salinity gradients, and kinetic energy), captured, and/or stored. In contrast to traditional electrical power plants, fuel for energy harvesters is naturally present. For example, temperature gradients exist from operation of a combustion engine, and in urban areas, large amounts of electromagnetic energy is present in the environment due to radio and television broadcasting. Thus, large-scale ambient energy, such as sun, wind, and tides is widely available; however, such energy may not be effectively captured with much efficiency or at low costs.
Even though some types of energy harvesters fueled by ambient energy may not produce sufficient energy to perform mechanical work, small amounts of power can be generated. Harnessing ambient mechanical vibrations to produce sustainable power sources may have several applications in aerospace and outer space, for example, where ambient mechanical vibrations are plentiful. Other applications that may be pursued include using scavenged energy to power remote wireless sensors that have applications in structural health monitoring (SHM), and also to power micro-electromechanical systems (MEMS), for example. Still further, energy harvesting may be useful when applied to small, wireless autonomous devices, such as those used in wearable electronics and wireless sensor networks.